ABSTRACT The study focused on influence of hidden costs in education on academic performance in public primary schools in Gatanga district. This mainly aimed at investigating the influence of extra school levies on academic performance, relationship of lunch expenses and academic performance, opportunity costs and its influence on academic performance, influence of transport costs on academic performance and relationship between expenditure on school uniform and academic performance in public primary schools.The study may contribute to the body of knowledge on influence of hidden costs in education on academic performance in public primary school. The findings of the study would be a source of knowledge to education and general leaders interested in hidden costs in education under free primary programme. The policy makers of the Ministry of Education and curriculum implementers would pay more attention to specific needs of pupils in public primary schools in Gatanga and provide relevant data and strategic that can be put in place to decrease or abolish hidden costs in education so as to encourage pupils from their areas to improve their academic achievement. Stakeholders of education would look into the possible ways of reducing inequalities in education for example engaging in income generating activities in schools in order to cater for these hidden costs. The study was based on education production function (EPF) as advocated by coleman, 1966 in psacharopolous and Woodhall (1985). In this theory academic achievement in the production function is seen as a function of many variables. The theory indicate that education process is seen as a production process where many inputs are expensed in a given ratio to produce good results (output). Its therefore clear that the quality of the output will be determined by level of inputs provided how well they are combined for maximum output and the quality of the inputs.In this study the academic achievement in the production process is a function of the hidden costs in education and hence are the inputs. If well catered for they are likely to produce the maximum output. This analysis on the education production function is about how inputs are transformed into outputs. The theory helps in examining the relationship between inputs and outputs in the teaching/learning process.The study was conducted in 30 public primary schools and adopted a descriptive survey design. The respondents included 30 head teachers, 120 teachers and 300 pupils. Stratified and simple random sampling procedures were used to select head teachers and teachers respectively. Data were collected using self administered questionnaires and interview guides. The data was analysed using descriptive statistics and content analysis. Statistical package for social sciences (SPSS) version 18.0 was used to analyse data. Findings of the study were that pupil who do not pay extra school levies, lunch expenses, opportunity costs, transport costs and school uniform all affect academic performance. Major recommendations were that government should intervene through disbursement of more funds to fully cover all these hidden costs in education. Measures should be put in place to ensure that while going after sees defaulters pupils are not forced out of school, the government through different stakeholders should try and combat the rise from the community by empowering the parents. Provision of school feeding programme and employment of enough teachers by the government to avoid overburdening the parents to employ their own.